1. Field of the Invention
This invention relates generally to a system and a method for controlling the combustion process in a continuous-type fuel combustion system. More specifically, this invention relates an improved system for regulating the air/fuel ratio in a gas combustion-type turbine system.
2. Description of the Prior Art
Gas combustion-type turbine systems like those manufactured by the assignee of this invention, Westinghouse Electric Company, are in common use for power generation purposes throughout the world.
A conventional gas turbine combustion system 10 is depicted in FIG. 1. In such a conventional system 10, a compressor fan 14 forces intake air into a chamber 16. System 10 further includes a plurality of combustion baskets 18, each of which have a combustion chamber 20 that is separated into primary and secondary combustion chambers. Each basket 18 is communicated, by known structure and controls, with a fuel supply 22 for supplying fuel to combustion chamber 20, as well as a number of fixed nozzles 24 for admitting pressurized fuel into combustion chamber 20.
To optimize the efficiency of system 10, and to keep the combustion process as clean and pollutant-free as possible, turbine system 10 includes a system 28 for regulating the air/fuel mixture that is provided to combustion chamber 20. As will be seen in FIG. 1, each basket 18 includes a transition piece 46 that defines a transition passage 44 between the combustion chamber 20 and a turbine intake area 48. The turbine intake area 48 is characterized by the stationary vane 11 that is shown in FIG. 1. As is also shown in FIG. 1, a butterfly valve 42 is provided for admitting pressurized air from chamber 16 to the transition piece 46, well downstream of the combustion chamber 20. When butterfly valve 42 is open, pressurized air bypasses chamber 16, thereby reducing the amount of air that is forced into the inlets 24 of combustion chamber 20. Accordingly, by opening butterfly valve 42, the air/fuel ratio in combustion chamber 20 is reduced. By closing butterfly valve 42, conversely, the air/fuel ratio in combustion chamber 20 can be increased.
A mechanical control linkage 40 is provided in conventional system 10 for opening and closing butterfly valve 42. As may be seen in FIG. 1, an external rotating ring 30 is provided outside housing 12 for movement on bearings 32. Each butterfly valve 42 is coupled to a control rod 31 that passes through a hole in housing 12. One tie rod 34 is secured to external sliding ring 30. A second tie rod 38 is secured to a top end of control rod 31. Tie rods 34, 36 are connected together by a ball pivot 36. Accordingly, when rotating ring 30 is shifted in one direction or another, it causes the control rods 31 for the respective gaskets 18 to turn to a desired extent in one direction or another, to control the operation of the respective butterfly valves 42.
Although regulating systems of the type depicted in FIG. 1 operate effectively, the systems tend to be expensive and time consuming to manufacture. Manufacture of such systems entails forming a number of holes in the housing, as well as positioning the control linkage that controls the respective butterfly valves. It is clear that a need exists for a simpler and less expensive air/fuel regulating system.